A MID-18TH CENTURY DAVIS QUADRANT (BACK-STAFF)
SKU: 228
Discount:
A MID-18TH CENTURY DAVIS QUADRANT (BACK-STAFF)
The Davis quadrant was used on ships to determine position at sea until the middle
of the 18th century.
It was used to measure the altitude of a celestial body, in particular the sun or moon.
When observing the sun, users kept the sun to their back.
It was a shadow instrument, looking directly into the sun was no longer necessary.
It was invented by John Davis (1550-1605), a British sailor who explored the west
coast of Greenland and discovered the Falkland Islands.
The Davis Quadrant has two arcs with graduations.
Large circle arc within scale 0° – 25° in segments of 5 minutes and readable per minute.
Small circle arc 0° - 65°-1°
It was a fairly accurate instrument.
With a little practice one could also measure on a swaying ship.
On the empty bone label the measure could be written down as a mnemonic.
Provenance:
This quadrant comes from the collection of Prof. Dr. Prestel (1809-1880).
The instrument has his name tag.
Michael August Friedrich Prestel was a German mathematician, meteorologist and cartographer.
(* Gottingen, 27 October 1809; † Emden, 29 February 1880).
As senior lecturer in mathematics and science he received the title of professor in 1867.
Prestel also was a teacher at the Academy of navigation and a member of the exams
committee for yachtsmen.
Size: total length 63 cm, width 25.5 cm.
SOLD TO THE USA
The Davis quadrant was used on ships to determine position at sea until the middle
of the 18th century.
It was used to measure the altitude of a celestial body, in particular the sun or moon.
When observing the sun, users kept the sun to their back.
It was a shadow instrument, looking directly into the sun was no longer necessary.
It was invented by John Davis (1550-1605), a British sailor who explored the west
coast of Greenland and discovered the Falkland Islands.
The Davis Quadrant has two arcs with graduations.
Large circle arc within scale 0° – 25° in segments of 5 minutes and readable per minute.
Small circle arc 0° - 65°-1°
It was a fairly accurate instrument.
With a little practice one could also measure on a swaying ship.
On the empty bone label the measure could be written down as a mnemonic.
Provenance:
This quadrant comes from the collection of Prof. Dr. Prestel (1809-1880).
The instrument has his name tag.
Michael August Friedrich Prestel was a German mathematician, meteorologist and cartographer.
(* Gottingen, 27 October 1809; † Emden, 29 February 1880).
As senior lecturer in mathematics and science he received the title of professor in 1867.
Prestel also was a teacher at the Academy of navigation and a member of the exams
committee for yachtsmen.
Size: total length 63 cm, width 25.5 cm.
SOLD TO THE USA